Document that it is possible to synchronise a PHP update with a deployment

[johnbillion]

Ref https://dashboard.altis-dxp.com/support/ticket/7081/, it's possible to synchronise a PHP update and a deployment (because the PHP update doesn't go live until the subsequent deployment) but this is not clear from the docs.

The "Requesting A Cloud Environment Update" section of https://docs.altis-dxp.com/guides/updating-php/ should be updated to make this clear.